Some 1,2,4-triazolo[4,3-c]pyrimidines are known to the art. Certain 3-amino-1,2,4-triazolo[4,3-c]pyrimidines are disclosed in the patents discussed below:
United Kingdom Pat. No. 859,287 discloses what are believed to be the compounds 3-amino-7-methyl-5-methythio-1,2,4-triazolo[4,3-c]pyrimidine and 3-amino-7-chloro-5-methyl-1,2,4-triazolo[4,3-c]pyrimidine.
United Kingdom Pat. No. 873,223 broadly describes 6-hydrazinylpyrimidines which may contain alkyl, substituted alkyl, alkenyl, cycloalkyl, alkylthio and halogen sustituents in the 2-, 4- and 5-positions. These pyrimidines are used as intermediates in the preparation of 1,2,4-triazolo[4,3-c]pyrimidines.
United Kingdom Pat. No. 898,408 discloses 3-amino-1,2,4-triazolo[4,3-c]pyrimidines which are substituted on the pyrimidine ring at the 5-position by an alkyl, alkylthio, or amino substituent, at the 7-position by an alkyl, halogen-substituted alkyl or halogen substituent, and at the 8-position by hydrogen or an alkyl or alkenyl substituent. This patent also broadly describes, as intermediates, 6-hydrazinylpyrimidines which may contain alkyl, alkylthio or amino in the 2-position, alkyl, substituted alkyl or halogen in the 4-position, and hydrogen, alkyl or alkenyl in the 5-position.
The following related articles disclose the synthesis of certain 1,2,4-triazolo[4,3-c]pyrimidines as intermediates in the preparation of 1,2,4-triazolo[1,5-c]pyrimidines and as potential branchodilators.
G. W. Miller et al., J. Chem. Soc., 1963, 5642, discloses 1,2,4-triazolo[4,3-c]pyrimidines which are substituted at the 3-position by amino or imino substituents, and on the pyrimidine ring by alkyl substituents or alkyl and alkenyl substituents.
G. W. Miller et al., J. Chem. Soc., 1963, 3357, discloses the compound 3-hydroxy-7-methyl-5-n-propyl-1,2,4-triazolo[4,3-c]pyrimidine.
W. Broadbent et al., J. Chem. Soc., 1963, 3369, discloses the compound 3-mercapto-7-methyl-5-n-propyl-1,2,4-triazolo[4,3-c]pyrimidine.
Still other 1,2,4-triazolo[4,3-c]pyrimidines are disclosed in the following articles and patent:
Shiho et al., Yakagaku Zasshi, 1956, 76, 804, discloses 1,2,4-triazolo[4,3-c]pyrimidines which are substituted at the 3-position by alkyl or phenyl substituents, and on the pyrimidine ring by both methyl and methoxy substituents.
Temple et al., J. Org. Chem., 1968, 33, 530, discloses the compound 8-amino-7-chloro-5-triazolo[4,3-c]pyrimidine-3(2H)-one.
D. J. Brown et al., Aust. J. Chem., 1978, 31, 2505, discloses 1,2,4-triazolo[4,3-c]pyrimidines which are substituted at the 3-position by hydrogen or an alkyl substituent, and on the pyrimidine ring by hydrogen and/or alkyl substituents.
D. J. Brown et al., Aust. J. Chem., 1979, 32, 1585, discloses 1,2,4-triazolo[4,3-c]pyrimidines which are substituted at the 3-position by hydrogen or an alkyl substituent, and on the pyrimidine ring at the 5-position by a halogen, hydrazino, methylthio or methyl substituent, and at the 7-position by a methyl substituent. This paper also describes the compound 6-hydrazinyl-4-methyl-2-methylthiopyrimidine.
U.S. Pat. No. 4,269,980 discloses 5-, 7- and 8-(optionally substituted-phenyl)-1,2,4-triazolo[4,3-c]pyrimidines. These compounds may be substituted at the 3-position by hydrogen or an alkyl substituent and are anxiolytic agents. This patent also describes, as intermediates, 6-hydrazinylpyrimidines which contain an optionally-substituted phenyl group in the 2, 4 or 5-position.